9.75 mpg! What Gives?

[Rebel_Horseman]

Here's the deal fellas (and ladies). Went to north Mississippi this weekend to pick up a laod of hay. Left Baton Rouge with a full tank of diesel and the low fuel light was glowing when I was rolling into Meridian, MS which is about 215 miles. I was pulling a 20+5 gooseneck trailer with an 8' neck and 2 12,000# dual-tire axles. As it sits, the trailer weighs 6,000#. I ran 75 with no A/C and just me and my room mate and our junk. That tank was 9.75 mpg. Coming back with 70 bales of hay (each bale is about 30-40 lbs) I got just barely over 9 mpg. Total trailer weight was around 8,800# running 70-75 mph. There was some fairly large hills but the truck seemed to downshift even on the smallest of hills even when pulling just the trailer unloaded. I bought a new fuel filter and plan on changing it this afternoon. The current filter has about 7,000 miles on it and the oil is about due for change as well. Every other tank I've ran an additive. Started with Red Line synthetic and last tank I added Stanadyne.

Can anyone explain why this truck is not even getting into the double digits on mpg?

Thanks
Reb [><]

PS: Sorry for the long post.

[ 01-06-2003: Message edited by: Rebel_Horseman ]</p>

[sdaver]

SOUNDS LIKE THE AERODYNAMICS OF HAY BALES IS NOT SO HOT............AND MAYBE A HEAD WIND :D DAVE

[AKDmax]

The dealer should be able to address the busy shift problem. You probably weren't in the "sweet spot" on the thottle at that speed, especially with that weight.

[ 01-06-2003: Message edited by: AKDmax ]</p>

[Rebel_Horseman]

AKDmax & Others:

What speeds do ya'll suggest towing at? My cousin's truck is identical and he can run 85 and still get 14 towing. He got that hauling a steel car trailer with a '64 Chevy 4x4 from Ohio to Mississippi.

Reb [&gt;&lt;]

PS: The '64 Chevy was mint condition with 34,000 original miles. I dind't ask any questions beyond that because I was scared I'd either get a warm fuzzy feeling or upset becasue it wasn't mine. :D

[pullinpower]

Rebel_Horseman,I pulled this same stretch of highway (memphis-baton rouge)with a daul axle gooseneck with a do-all,about 18K worth going to baton rouge and got around 12mpg I think you should get the updates done to the tranny and go for a power enhancer(juice,pcm mod,maximiser etc.),Rough stretch of highway also.Makes you wanna upgrade the shocks even more after that trip.

P.S When is the last time you changed the fuel filter?

[Rebel_Horseman]

The fuel filter has about 7,000 miles on it and I'm going to change it again this afternoon. The roads weren't too bad but they was definately room for improvement. I'm still saving up for a programmer or other power mod. I heard Hypertech is coming out with a programmer similar to the Diablo that is being discussed for about $300-400 but it will only give you either 30 or 60 hp (I don't remember which).

Reb [&gt;&lt;]

[Runaway]

Any chance a brake was hanging up on the trailer?

[Heartbeat Hauler]

I have experienced the same thing. When I first got the truck I was gettin' about 15 mpg towing the trailer (9000lb fiver). Now I'm gettin' about 9 mpg. I just had the fuel filter replaced and the oil filter changed. The only real difference is that I added an AMSOIL air filter. I will admit that the truck spent a good bit of the time at about 3000 rpm because of that overdrive issue, but I never had this problem before and I have made this same trip numerous times with the same setup. What Gives is right.
JP

[AKDmax]

Towing my 8,000 lb. TT I found that anything over 65 severely dropped my mileage. Not that bad though. Try the shift busyness update first and see if that helps. Be careful about mentioning the hypertech programmer, you might start another ruckus in TDP. ;)

[gardnerteam]

My experience is than anytime you push a D/A over 70 mph, your mileage will go down in a inproportionate amount to your speed, expecially when pulling a load. Ran 2200 miles a couple of weeks ago with a loaded triple axle with a gross of 25,000 (25000). At 70 indicated mph mileage was about 9, at 75 indicated it dropped to about 8 or slightly less. When I set the cruise at 65 (speedometer, which is 9% off due to 285 tires), I got 11.5, which I consider to be good considering the weight, tire size, and few grades I pulled (Grapevine in Cal 2 ways, Cascades in Oregon. If you want mileage, slow down. Yes, I know it is hard. The only way I got it done was the constant threat of CHP slowing the trucks and vehicles with trailers to below 62 mph. When I run in Idaho and Utah at 75 mph, I get about 8 with the same load.

[TBC]

I have kept records since day 1 on my 01 D/A. I am getting an overall average of 13.6 with a low of 8.1 and high of 20.3. This is towing 8800 lb TT, city driving, and highway. I don't baby it but the faster I drive the more the MPG drops. There is a big diff between 65 and 70 or 75 towing or empty. There was an article on a website a while back about fuel economy with a diesel and on average for every 10 MPH above 60y you drop 3 MPG.

Every time I read about poor mileage it is always tied to high speed driving. To the best of my knowledge no manufacturer builds a vehicle that will get better mileage at higher speeds. Want better mileage, slow down. When towing it takes fuel to make power to tow heavy loads therefore lower fuel economy. I will take my diesel over any gas engine for towing, especially when a 454 towing the same trailer got 5 MPG low and absolute downhill tailwind best of 8.5 MPG and no wheres near the power.

My $.02 worth.

Tom

[Kennedy]

I've had mine BELOW 7mpg :eek:

FWIW, tandem duallys pull like crap, and ride like crap.

[Rebel_Horseman]

Thanks for all the help folks. Next time I make a run I'll try and run it at 65 to see what happens (the key word is try). Hopefully within the next week or so I can get the busy shift problem fixed like I asked it to be fixed the first time I went to the dealer.

Reb [&gt;&lt;]

[N.E. TMRPR]

Made a trip to TN about a month ago with a four horse aluminum gooseneck with three head on board. I guess trailer and load to be around 10,000 to 11,000. I ran at 75 to 80 almost all the way. The trip was 1060 miles in 17 hours. This averages with fuel stops to about 63 mph. My fuel mileage was 11.8 mpg. I find if I keep my speed going up the hills it very rarely downshifted on me. I have to say my truck has always been good on fuel and will give me 18.8 mpg when running bobtail at 80. It is a 2001 cc 4wd that is all stock. One last thing is to check the air filter. I have collapsed three on trips when they have gotten loaded up. I have put 8 filters on my truck in 71,000 miles.